General image forming (recording) apparatuses, such as printers, facsimile machines, copiers, plotters, or multi-task machines having plural such functions, include a recording head composed of liquid ejection heads that eject liquid droplets of ink so as to form images. During image formation (used synonymously with recording, printing, and imaging), the image forming apparatuses cause the liquid droplets of the ink to adhere to a medium, while transferring the medium (hereinafter referred also to as a sheet, but it does not limit the material; also, it is used synonymously with a medium to be recorded, a recording medium, a transfer member, a recording paper, etc.).
Note that the “image forming apparatuses” refer to apparatuses that eject liquid onto a medium such as a paper, a thread, a fiber, a fabric, leather, metal, a plastic, glass, wood, and a ceramic so as to perform the image formation. Furthermore, the “image formation” refers to forming on the medium not only meaningful images such as characters and graphics, but also meaningless images such as patterns (merely, ejection of liquid droplets). Furthermore, the “ink” is not limited to narrowly-defined ink and is not particularly limited so long as it is liquid when ejected. For example, the ink refers also to a DNA sample, a resist, a pattern material, a resin material, etc.
In such image forming apparatuses, recording speed (printing speed) and image quality have been improved as the processing capacity of information processing apparatuses such as personal computers increases. In order to improve the recording speed, a recording head is formed in an elongated shape by which the number of nozzles is increased, or plural recording heads are connected to each other in line form. Furthermore, in order to improve the image quality, nozzles (heads) are arranged in multiple rows so as to use as many ink colors as possible. Compared with those of conventional apparatuses, recording apparatuses having such recording heads are upsized, which in turn increases their manufacturing costs. Therefore, it is expected to further downsize recording heads and carriages (of a serial type) having such recording heads and reduce their manufacturing costs.
Meanwhile, a flexible printed circuit (hereinafter referred to as a “FPC”) is used to transmit electric signals of recording information, etc., from a recording apparatus main body to recording heads (see Patent Document 1).
Patent Document 1: JP-A-10-109410
As a conventional head configuration using the FPC, Patent Document 2 describes one in which the FPCs are provided facing both side surfaces perpendicular to a nozzle surface. Each of the FPCs has one end connected to the actuator of a recording head and the other end connected to a connector electrically connected to the recording apparatus main body.
Patent Document 2: JP-A-2002-046256
Furthermore, Patent Document 3 describes a recording apparatus having a flexible wiring board that serves as one transformed into two shapes. Therefore, a pair of the flexible wiring boards is provided to correspond to respective connection parts of a recording head, while the wiring boards face each other at connections with connection parts. The flexible wiring boards are folded at almost a right angle relative to the longitudinal direction between the recording head and a driving circuit board and folded back 180 degrees.
Patent Document 3: JP-A-2002-321371
However, according to the above configuration of Patent Document 2, connector parts are also caused to face each other together with the FPCs, which in turn makes it impossible to reduce the width (in width direction) of the recording head.
In addition, according to the above configuration of Patent Document 2, the flexible wiring board is folded back to use the same part so as to reduce the cost of parts. However, the downsizing of a carriage including the recording head and the reduction of the cost of the parts accompanied by the downsizing of the flexible wiring board are insufficient.
Moreover, as shown in FIG. 1, in the case of a line-type head unit 1000 for use in a line-type image forming apparatus in which plural short heads 1001 are arranged in a staggered manner and held on a head supporting member 1002, the head unit 1000 itself is large. As a result, the image forming apparatus including the head unit 1000 becomes extremely large. The length “L” of the head unit 1000 depends on the size of a recording medium to be used in the image forming apparatus. On the other hand, the width “W” of the head unit 1000 does not depend on the recording medium, but directly influences the size of the image forming apparatus regardless of the size of the recording medium. Because the head 1001 has the width “w” in this example, the width “W” of the head unit 1000 becomes at least “2w.” Therefore, the reduction of the width “W” of the head unit 1000 is accompanied by the reduction of the width “w” of the head unit 1001.
Thus, it is important to reduce the width of the head unit so as to downsize the line-type image forming apparatus main body, and it is desired that the width of the heads constituting the head unit be reduced to downsize the recording head. In a serial-type image forming apparatus as well, if the width of the recording head is large, the width of a scanning carriage becomes large, which in turn disturbs the downsizing of the image apparatus main body and high-speed printing. Therefore, the reduction of the width of the heads is desired.